Compressor



K. A. DARow July 9,1957

COMPRESSOR Filed Aug. so, 1954 [n Venter Ms Attorney.

United States lPatent COMPRESSOR Kenneth A. Darrow, Sprakers, N. Y.,assignor to General Electric Company, a corporation of N ew -YorkApplication August 30, 1954, Serial No. 452,935

2 Claims. (Cl. 230-114) This invention relates to compressors and moreparticularly to a method and apparatus for eliminating pulsation in suchcompressors.

A compressor in which pulsation is eliminated is desirable to provide aneicient machine. Pulsation is a serious problem in centrifugal or axialflow compressors because it reduces compressor performance greatly atlow rates and makes continuous operation untenable. Such pulsationoccurs when fluid flow becomes completely separated along the length ofthe flow passages in both the impeller and diffuser. The vibrationswhich are caused by such pulsation are suicient in a large compressor todestroy the machine.

Accordingly, it is an object of my invention to provide an improvedcompressor which has a long, useful operating range.

It is another object of the invention to provide an improved ycompressorin which high eticiencies are maintained at the low flow range near orbelow the normal pulsation point.

It is a further object of the invention to provide a novel method toextend the operating range in a cornpressor.

In carrying out my invention in one form, a constant fluid flow ismaintained through the compressor diffuser by the addition of secondaryair adjacent the impeller to supply air to the diffuser entrance.

These and various other objects, features and advantages of theinvention will be better understood from the following description takenin connection with the accompanying drawing in which:

Fig. 1 is a sectional view of a centrifugal compressor which embodies myinvention;

Fig. 2 is a bottom plan view taken along lines 2-2 of Fig. l; and

Fig. 3 is a `sectional view similar to Fig. l with the air inlets in anopen position.

In Fig. 1 of the drawing, a centrifugal compressor is shown generally atwhich comprises a casing 11 to define a chamber 12 therein. An air inletor aperture 13 is centrally disposed in the upper wall of casing 11. Acentrifugal blower impeller 14 with a plurality of curved blades 15thereon is mounted on a shaft 16 in axial alignment with inlet 13. Shaft16 is connected to a suitable source of power, such as an electric motor(not shown). Impeller 14 is provided with a back wall 17 and a forwardWall 18 which extend laterally therefrom to form a diffuser 19 which maybe of the vane or vaneless type. `A plurality of apertures 20 arelocated in wall 17 adjacent the free end of impeller 14 to admitsecondary air near the impeller tip and the diifuser entrance. A member21 with a pair of opposed apertures 22 near its periphery is mounted onthe outside of wall 17 by means of an upstanding ange 23 thereon throughwhich bolts 24 are secured. Member 21 is also provided with two pairs ofopposed brackets 25 on its outer surface to retain a sliding closuremember 26. As it is best shown in Fig. 2, member 26 is provided with acentral aperture 27 through which shaft 16 extends. An aperture 28 islocated at each of the opposite ends of member 26 for the admission ofsecondary air.

A control device 29 which operates member 26 comprises a casing 30 witha piston 31 therein to move a connecting rod 32. Rod 32 may be connectedto member 26 by any suitable means, such as, for example, a bolt 33 anda nut 34. Piston 31 is connected to the opposite end of cylinder 30 by aspring 35. Movement of piston 31 within cylinder 30 is controlled by aPitot tube 36 which is positioned in air inlet 13. Tube 36 comprises aninner tube 37 with an inlet 38 to measure the total pressure head and anouter tube 39 with an inlet 40 to measure the static pressure head.'I'ube 37 is connected to the spring side of cylinder 30 while tube 39is connected to the opposite side of piston 31.

In Fig. 3, centrifugal compressor 10 is shown with apertures 22 and 28in alignment to admit secondary air through apertures 20. This secondaryair is pumped by the injector action of the air which ows from theoutlet of impeller 14 to diffuser 19 to provide a constant owtherethrough. The open position of apertures 22 and 28 is attainedduring separation of the fluid from the wall of the flow passage toprevent pulsation in compressor 10.

In the operation of compressor 10, centrifugal action of impeller blades15 drives air from inlet 13 downwardly and outwardly towards the innerwall of casing 11. Member 26 closes apertures 22 until the fluid beginsto separate from the wall of diffuser 19. A decrease in the totalpressure head which is caused by a change in flow through inlet 13 istransmitted through tubes 37 and 39 to change the differential pressurein cylinder 30 to move piston 31 outwardly. Piston 31 controls member 26through connecting rod 32 to change the area of apertures 22--28. Thus,a varying flow of secondary air in the necessary amount is admitted tothe back of impeller 14 to provide an essentially constant diffuser Howat a flow point where separation will not occur. Compressor 10 utilizespumping action of the back of impeller 14 and ejector action of the airwhich leaves impeller 14 to furnish a secondary diffuser How. Areduction in the fluid ow through impeller 14 requires additionalsecondary air to provide a constant diifuser ow.

As will be apparent to those skilled in the art, the

f objects of my invention are attained by the use of a constant fluidflow through the diffuser which is provided by the addition of secondaryair adjacent. the impeller.

While other modifications of this invention and variations of apparatuswhich may be employed within the scope of this invention have not beendescribed the invention is intended to include all such as may beembraced within the following claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A compressor comprising a casing having an air inlet therein, animpeller within said casing arranged to receive air from said inlet, adiffuser adjacent the periphery of said impeller arranged to receive airfrom said impeller, secondary air apertures adjacent said impeller,adjustable closure means normally closing said apertures, said closuremeans comprising a member having at least one aperture therein enclosingsaid secondary air apertures, a second member normally closing theaperture of said first member, and means responsive to changes in airinlet pressure to adjust said adjustable closure means.

2. In a centrifugal compressor the combination comprising, a casinghaving an inlet therein, an impeller in said casing, a diffusersurrounding said impeller and arranged to receive air therefrom, saidcasing having an opening therein to admit air to the back of saidimpeller and near the impeller tip and the diffuser inlet, and meansresponsive to the change of air pressure in said Patented July 9, 1957 linl'e'tv to adnit air through' said opening to said diusertcrrn'aintair1- a' wnstant' ow'therein:

Refernces Cited the lepf this patent v,

UN'IIEDSTATES PTENTSi Y 5 1,089,665 Pagel .;g- 111311210;19.131'i IrwinIuly 14, 1931 Browne( Feb: 1-5", 19441 Loss May 17, 1949 Klein et al.Nov. 24, 1953 Muhlberg Sept. 28, 1954

